1. Field of the Invention
The present invention relates generally to diphenylhexafluoropropane derivatives and, more particularly, to derivatives wherein various groups are attached to the para-position on the phenyl rings of the diphenylhexafluoropropane by way of a carbon or silicon attachment.
2. Description of the Background Art
Diphenylhexafluoropropane is a very versatile compound which basically consists of two phenyl rings which are attached on opposite sides of the number two carbon of hexafluoropropane. In the past, a number of different derivatives of diphenylhexafluoropropane have been produced by attaching various different functional groups at either the para- or the meta-positions on the phenyl rings. These derivatives have proven to be useful intermediates in the synthesis of thermally stable resins for use in high temperature structural composites.
Diphenylhexafluoropropane compounds have been produced where various different functional groups, such as ethynyl groups, amino groups, or halogens, are attached to the phenyl rings at the meta-position by way of carbon or nitrogen linkages. As is well known, the specific isomeric form of chemical precursors and intermediates is an important factor in determining the final characteristics and performance of the desired chemical product. Accordingly, it has been desirable to also prepare diphenylhexafluoropropane derivatives in which the functional groups are attached to the phenyl rings at the para-position instead of the meta-position.
Diphenylhexafluoropropane compounds having an ethynyl group or a substituted ethynyl group attached at the para- or meta-position have been developed and are disclosed in U.S. Pat. No. 4,374,291 and U.S. patent application Ser. No. 466,271, respectively, both of which are assigned to the present assignee. However, other para-substituted diphenylhexafluoropropane derivatives which have been developed in the past and which are presently available all include an oxygen or sulfur linkage between the functional group and the phenyl ring. The attachment of the functional groups to the para-position on the phenyl rings via sulfur or oxygen results in a relatively flexible linkage which, in turn, tends to produce relatively flexible polymer products. Although flexible high temperature polymers are well suited for a variety of applications, it is many times desirable to provide thermally stable resins which have increased rigidity. Further, sulfur and oxygen linkages in polymer resins are more susceptible to oxidative degradation or breakdown resulting in premature deterioration of the polymer in which the sulfur or oxygen linked diphenylhexafluoropropane derivative is incorporated.
Therefore, there is a present need to provide para-substituted diphenylhexafluoropropane derivatives which can be used as alternate polymer precursors to meta-substituted derivatives and which do not include a sulfur or oxygen linkage between the para-substituted group and the phenyl rings.